Method of forming of a semiconductor film, method of manufacture of a semiconductor device and a semiconductor device

Abstract

This invention provides a method of forming semiconductor films on dielectrics at temperatures below 400° C. Semiconductor films are required for thin film transistors (TFTs), on-chip sensors, on-chip micro-electromechanical systems (MEMS) and monolithic 3D-integrated circuits. For these applications, it is advantageous to form the semiconductor films below 400° C. because higher temperatures are likely to destroy any underlying devices and/or substrates. This invention successfully achieves low temperature growth of germanium films using diboran. First, diboran gas is supplied into a reaction chamber at a temperature below 400° C. The diboran decomposes itself at the given temperature and decomposed boron is attached to the surface of a dielectric, for e.g., SiO 2 , forming a nucleation site and/or a seed layer. Second, source gases for semiconductor film formation, for e.g., SiH 4 , GeH 4 , etc., are supplied into the chamber, thereby forming a semiconductor film.

1. A method of forming a semiconductor film on an insulating film formed on a semiconductor or an insulating substrate, wherein a diboran gas or a diboran/silane mixed gas is supplied to a reaction chamber before forming the semiconductor film, wherein the method comprises the following sequential steps:
 (i) establishing temperature of a substrate at a first temperature; 
 (ii) supplying the diborane or diboran/silane mixed gas into the reaction chamber; 
 (iii) establishing temperature of the substrate at a second temperature without supplying reaction gases into the reaction chamber; and 
 (iv) supplying a gas including GeH 4  and/or SiH 4  into the reaction chamber to form the semiconductor film. 
 
     
     
       2. The method of forming a semiconductor film as recited in  claim 1 , wherein the semiconductor film is mainly composed of germanium. 
     
     
       3. The method of forming a semiconductor film as recited in  claim 1 , wherein the diboran gas or diboran/silane mixed gas are diluted by hydrogen. 
     
     
       4. The method of forming a semiconductor film as recited in  claim 1 , wherein a product of a time of exposure and a partial pressure of the diboran gas or diboran/silane mixed gas during film formation is more than 20 mTorr·min. 
     
     
       5. The method of forming a semiconductor film as recited in  claim 1 , wherein the insulating film is formed below 400° C. 
     
     
       6. The method of forming a semiconductor film as recited in  claim 1 , wherein the first temperature is higher than the second temperature. 
     
     
       7. The method of forming a semiconductor film as recited in  claim 1 , wherein the first temperature is 350° C. 
     
     
       8. The method of forming a semiconductor film as recited in  claim 1 , wherein the gas supplied in step (iv) comprises at least one of PH 3 , B 2 H 6  or AsH 3  mixed with GeH 4 .